Democratic Sen. Jeff Merkley of Oregon has a 16- to 20-point lead on two Republican opponents, according to an internal poll obtained by POLITICO.

Merkley leads Monica Wehby, 52 percent to 32 percent, among likely voters, according to a survey Benenson Strategy Group conducted on his campaign’s behalf.

D.C. Republicans have touted Wehby, a brain surgeon, as the kind of candidate who could put blue Oregon in play against Merkley. She was the subject of a weekend Associated Press feature outlining factors that could bolster her, including Obamacare’s rocky debut in Oregon; traditionally lower Democratic turnout in many states in midterms; and Wehby’s fundraising potential.

But there’s no guarantee Wehby will qualify for the November ballot. Among likely voters in the state’s all-mail Republican primary next month, Wehby (22 percent) and state Rep. Jason Conger (24 percent) run neck-and-neck, according to the poll.

More than half of likely GOP voters said they were undecided.

Merkley leads Conger by a similar margin in the general, 50 percent to 34 percent, according to the survey.

“Regardless of the opponent, Sen. Merkley starts out at or above the 50 percent threshold needed to win a fall election,” pollsters Pete Brodnitz and Mike Gehrke wrote in a memo.